1. Field of the Invention
The present invention relates to a camera system having a camera body with a power supply and, more particularly, to a camera system having a camera body with a power supply for supplying power to an accessory, such as a lens, a strobe, a data back (for putting photographic information on fill of the camera system) or a remote control, of the camera.
2. Description of the Related Art
In a conventional camera, in the case of providing power to an accessory attachable to such a camera, by connecting the camera body directly to the accessory without special control, the output of the camera body is arranged so as to be able to output power to the connection contact points of the camera body and the accessory. However, in this kind of device, the provision of power to the accessory is not under the control of the camera body. Accordingly, the power supply is output to normal connection contact points of the camera body and the accessory, and at the time of installation of the accessory to the camera body, the accessory comes into contact with the contact points for communication use and other electrical contact points of the camera body. In particular, by the accessory coming into contact with contact points for a power supply of a motor, etc., because the output impedance is rather low, it is possible for circuits of the accessory to be damaged.
A device for improving on this feature is disclosed, for example, in Japanese Laid-Open Patent Publication 62-175. In this conventional device, an installation of an accessory to a camera body is detected and a first power supply for communication use is provided. If proper communication is established, a second power supply for a motor and the like of the accessory is provided to the accessory.
This conventional device is effective in avoiding the above-mentioned disadvantage, but if communication is not established, the second power supply for the motor and the like of the accessory is not provided, so that no power is provided on the accessory side (to the accessory) before communication is established. Accordingly, using the second power supply on the accessory side as the power supply for other circuits is not possible. Moreover, in a situation such as frequently performing communication, if communication error or data alteration occurs, there is a risk of power supply cutoff.